Why Some Cities Are Getting Drier as Skyscrapers Rise

By Christina Larson, Environment: Yale Magazine. Posted February 17, 2009.

Now, as planners must account for the impact of urban growth on climate, it may be time to return to more site-specific approaches -- not for nostalgic reasons but as a matter of common sense in mapping the future. "A century ago, people lost centuries of knowledge about how to adapt to climate when we began using technology to overcome natural barriers," says Roberto Sánchez-Rodríguez, a professor of environmental sciences at the University of California, Riverside. "But not every city has to strive to look like Los Angeles or New York today."

For the last decade, Sánchez-Rodríguez has been at the forefront of efforts to bring science to bear on real-world decision-making. Among other projects, he has advised planners in Tijuana, Mexico, which a decade ago was devastated by flooding caused by El Niño. "A lot of knowledge has already been generated about environmental planning and how cities affect climate," he says, "and yet so little of this knowledge is used by planners on a daily basis." The collaboration has given him a greater appreciation for the concerns of city officials, helping him to tailor his advice. City planners, who must consider the short-term needs of their constituents, are in general not versed in ecology and climate science. Likewise, ecologists largely are not trained in what issues city planners must confront. "To work together successfully, you have to be very strategic in how you use these people's time, how to present conclusions," he says. "There needs to be someone who can act as an interface between the two domains of knowledge." 

Urban density, and the rising global middle class moving to swelling cities, has lately gotten a bad rap -- the "crowded" part of Thomas Friedman's book title warning that the Earth is becoming Hot, Flat, and Crowded. But because Shenzhen and Manhattan aren't likely to be torn down anytime soon, it may be helpful to rejigger our thinking. "Urban areas should be where environmental policy starts, not where it ends," says Margaret O'Mara, a visiting assistant professor of urban history at the University of Washington. "Scientists and environmental planners need to consider landscapes like Rio de Janeiro, not only Amazon rainforests."

She points out that there may be opportunities in inevitable urban growth, including the possibility of scaling up green-friendly technologies that urban density allows. It will be a simpler matter, for instance, to install new units designed to calibrate household energy usage, or recycle wastewater, in a towering Beijing apartment complex than in 2,000 single-family homes. "We need to think of cities not only as environmental problems, but as a component of environmental solutions; they have to be," says O'Mara.

The fast-rising skylines in regions like the Pearl River Delta -- and the recognition of the impact they have on climate -- mean neither a death sentence nor deliverance, but must be seen as a force, like gravity, that scientists and planners should find a way to work with wisely. Or, as The Granite Garden put it nearly 25 years ago: "Civilizations and governments rise and fall; traditions, values, and policies change; but the natural environment of each city remains an enduring framework within which the human community builds."

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Christina Larson is a journalist focusing on international environmental issues. Her reporting has brought her to seven provinces across China, as well as cities and villages in Cambodia, Vietnam, Thailand, and Greece. Her writing has appeared in The New York Times, The New Republic, Christian Science Monitor, China Environment Series, and The Washington Monthly, where she is a contributing editor.

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